Martin, I worked on a 30 m site with sheet metal ground plane last year. It got to 45 deg C several times during the summer and it was HOT. I also got snowblind from the glare. This ground plane was spot welded along the seams, had great site attenuation characteristics and seemed to hold up well - until the flash flood this winter. The rushing water picked up a third of the galvanized sheets and moved them 30 - 40 meters down stream. The mesh ground plane on the nearby 10 meter site got dirty but was otherwise unharmed.
I suppose if the metal had been bolted into concrete or if the pad had been higher the site would not have suffered, but I wonder whether the added expense over using mesh is worth it. Also, the sheet metal ground plane got HOT (did I mention how hot it got?)
